to secure the Java OS, access to the core applets is restricted while the device is in use. when you change certain settings, the core applets themselves havent been changed "on the fly", thus requiring the applets to be shut down before the new settings can be applied... this is where the hard reset/battery pull comes into play. it enhances the stability of the OS.

likening it to MS Windows in the same order as above...
1 = putting the computer into sleep mode
2 = installing new software and is usually usable immediately after installation
3 = installing drivers and having to reboot to utilize the new drivers

it's a crappy analogy, but the best i can do putting it to something more familiar.